Process for producing O,O-diesters of thiophosphorus acid

ABSTRACT

A process for producing thiophosphorous acid-O,O-diesters from corresponding phosphorous acid diester chlorides and hydrogen sulfide, in which process the acid acceptor used is ammonia. The thiophosphorous acid diesters obtained are suitable as intermediates for producing lubricant additives, fungicides or pharmaceutical products.

This is a divisional application of application Ser. No. 164,701, filedJune 30, 1980, now U.S. Pat. No. 4,341,722, issued July 27, 1982.

The present invention relates to a novel process for producingthiophosphorous acid diesters, to novel thiophosphorous acid diesters,and to their use as intermediates.

The manner of producing thiophosphorous acid diesters from phosphorousacid diester chloride and hydrogen sulfide is known for example from theU.S. Pat. No. 2,805,241, wherein the acid acceptors used are tert.nitrogen bases, such as dimethylaniline, triethylamine or pyridine. Thecommercial carrying out of this process is however costly since the useof relatively expensive tert. amines necessitates the filtration of theamine hydrochlorides and the subsequent recovery of the employed amines.

The subject matter of the present invention is a process for producingthiophosphorous acid diesters on a large commercial scale, in a simplemanner and also in a yield higher than that hitherto obtained. Theinvention relates to a process for producing thiophosphorous aciddiesters of the formula ##STR1## wherein R₁ and R₂ independently of oneanother are each C₁ -C₁₈ -alkyl, C₅ -C₁₂ -cycloalkyl, phenyl or C₇ -C₉-aralkyl each of which is unsubstituted or is substituted by one or twoC₁ -C₁₂ -alkyl groups, or R₁ and R₂ are each C₂ -C₁₀ -alkoxyalkyl or C₃-C₂₀ -alkoxycarbonylalkyl, or R₁ and R₂ together are a bivalent radicalof the formula II ##STR2## wherein n is nought or 1, and R₃, R₄, R₅ andR₆ independently of one another are each hydrogen, C₁ -C₄ -alkyl,cyclohexyl or phenyl, and R₃, when n is nought, is also --CH₂ Z, inwhich Z is --XR₁₀, --N(R₁₁)R₁₂, --S--P(S)--(OR₁₀)₂ or a group of theformula III ##STR3## wherein R₁ and R₂ have the given meanings, X isoxygen or sulfur, and R₁₀, R₁₁ and R₁₂ independently of one another areeach C₁ -C₁₈ -alkyl, C₅ -C₁₂ -cycloalkyl, phenyl or C₇ -C₉ -aralkyl eachof which is unsubstituted or is substituted by one or two C₁ -C₁₂ -alkylgroups, or R₁₀, R₁₁ and R₁₂ are each C₂ -C₁₀ -alkoxyalkyl or C₃ -C₂₀-alkoxycarbonylalkyl, and R₇ and R₈ independently of one another areeach hydrogen, C₁ -C₄ -alkyl, cyclohexyl, phenyl, nitro, cyano, C₂ -C₁₉-alkoxycarbonyl, C₂ -C₁₈ -alkanoyl, or a group of the formula (R₉ --O)₂--P(O)--, in which R₉ is C₁ --C₁₈ -alkyl, or R₇ and R₈ together are2-butenylene or 2-pentenylene, which process comprises reacting acompound of the formula ##STR4## wherein R₁ and R₂ have the meaningsgiven above, with hydrogen sulfide in the presence of ammonia.

The ammonia in this process surprisingly acts as an acid acceptor, anddoes not react in the expected manner with the P--Cl starting materialof the formula IV.

Preferably, ammonia gas and hydrogen sulfide gas are introduced at atemperature of -10° to +40° C., particularly +5° to +20° C., into asolution of a compound of the formula IV in an inert organic solvent.The flow of gas can be so finely regulated that the H₂ S and NH₃consumption corresponds approximately to the stoichiometric amounts. Anexcess of H₂ S is however possible. All solvents which are inert to thereactants are suitable, for example: aliphatic hydrocarbons, such asligroin, special gasoline or petroleum ether; cycloaliphatichydrocarbons, such as cyclohexane; aromatic hydrocarbons, such asbenzene, toluene or xylene; chlorinated hydrocarbons, such as methylenechloride or chlorobenzene; ethers, such as diethyl ether, dioxane ortetrahydrofuran; and also dimethylamide and dimethylsulfoxide. Solventspreferably used are nonpolar solvents having a boiling point in therange of 40°-150° C.

The pressure at which the process according to the invention isperformed is not critical; preferably however it is not greatlydifferent from normal pressure.

In the formula I, the substituents R₁ and R₂ can have identical ordifferent meanings. Compounds in which R₁ and R₂ are identical arepreferred.

As C₁ -C₁₈ -alkyl, R₁, R₂, R₉, R₁₀, R₁₁ and R₁₂ are for example methyl,ethyl, n-propyl, isopropyl, n-butyl, sec-butyl, tert-butyl, n-hexyl,2-ethylhexyl, 6-methylheptyl, n-octyl, straight-chain or branched-chainnonyl, decyl, dodecyl, tridecyl, tetradecyl or octadecyl. Preferredalkyl groups having 3-13 C atoms.

As C₅ -C₁₂ -cycloalkyl and particularly as C₆ -C₁₀ -cycloalkyl, R₁, R₂,R₁₀, R₁₁ and R₁₂ can be for example: cyclopentyl, cyclohexyl,cyclooctyl, cyclodecyl or cyclododecyl. Cyclohexyl is preferred.

If R₁, R₂, R₁₀, R₁₁ and R₁₂ are phenyl or C₇ -C₉ -aralkyl, thesearomatic radicals can be substituted by one or two alkyl groups having1-12 C atoms, preferably 1-9 C atoms. Examples of alkyl substituents ofthis kind are methyl, ethyl, isopropyl, n-butyl, sec-butyl, tert-butyl,tert-amyl, n-hexyl, n-octyl, 1,1,3,3-tetramethylbutyl or1,1,3,3,5,5-hexamethylhexyl. When R₁, R₂, R₁₀, R₁₁ and R₁₂ are C₇ -C₉-aralkyl, it can be α,α-dimethylbenzyl, preferably β-phenylethyl andparticularly benzyl.

Where R₁, R₂, R₁₀, R₁₁ and R₁₂ are C₂ -C₁₀ -alkoxyalkyl, the alkylmoiety can contain 1-3 C atoms, and the alkoxy moiety 1-8 C atoms, forexample in methoxymethyl, ethoxymethyl, 2-methoxyethyl, 2-ethoxyethyl,2-n-butoxyethyl, 3-n-butoxyethyl, 2-octoxyethyl or methoxypropyl. To bementioned in particular are compounds in which R₁, R₂, R₁₀, R₁₁ and R₁₂as alkoxyalkyl contain 3-6 C atoms.

As C₃ -C₂₀ -alkoxycarbonylalkyl wherein the alkyl moiety contains 1-3 Catoms and the alkoxycarbonyl moiety 2-18 C atoms, R₁, R₂, R₁₀, R₁₁ andR₁₂ are for example: methoxycarbonylmethyl, propoxycarbonylmethyl,butoxycarbonylmethyl, octoxycarbonylmethyl, dodecoxycarbonylmethyl,octadecoxycarbonylmethyl, methoxycarbonylethyl, ethoxycarbonylethyl,octadecoxycarbonylethyl or methoxycarbonylpropyl. Preferably, R₁, R₂,R₁₀, R₁₁ and R₁₂ contain as alkoxycarbonylalkyl 4-10 C atoms.

If R₃, R₄, R₅, R₆, R₇ and R₈ are C₁ -C₄ -alkyl, they are for example:methyl, ethyl, n-propyl, isopropyl, n-butyl, sec-butyl or tert-butyl.

R₇ and R₈ as C₂ -C₁₉ -alkoxycarbonyl are for example: methoxycarbonyl,ethoxycarbonyl, butoxycarbonyl, hexoxycarbonyl, octoxycarbonyl,dodecoxycarbonyl or octadecoxycarbonyl. Preferred alkoxycarbonyl groupscontain 2-9 C atoms.

R₇ and R₈ as C₂ -C₁₈ -alkanoyl can be for example: formyl, acetyl,butyryl, hexanoyl, octanoyl, dodecanoyl or octadecanoyl. C₂ -C₈-alkanoyl groups are preferred.

n is nought or 1. Compounds of the formula I to be emphasised are thosewherein n is 1.

When R₃ is a group of the formula III, only one such group may becontained in the molecule.

The process is suitable especially for compounds of the formula Iwherein R₁ and R₂ independently of one another are each C₃ -C₁₃ -alkyl,C₆ -C₁₀ -cycloalkyl, phenyl or C₇ -C₈ -aralkyl each of which isunsubstituted or is substituted by one or two C₁ -C₄ -alkyl groups, orR₁ and R₂ are each C₃ -C₆ -alkoxyalkyl or C₄ -C₁₀ -alkoxycarbonylalkyl,or R₁ and R₂ together form a radical of the formula II in which R₃, R₄,R₅ and R₆ independently of one another are each hydrogen or C₁ -C₄-alkyl, and R₇ and R₈ independently of one another are each hydrogen, C₁-C₄ -alkyl, cyclohexyl, phenyl, nitro, C₂ -C₉ -alkoxycarbonyl or C₂ -C₈-alkanoyl, or R₇ and R₈ together are 2-butenylene or 2-pentenylene, andn is nought or 1; and for those compounds wherein R₃, if n is nought, isadditionally --CH₂ --Z, in which Z is --XR₁₀, --N(R₁₁)R₁₂,--S--P(S)(OR₁₀)₂ or a group of the formula III, and R₁₀, R₁₁ and R₁₂independently of one another are each C₁₋₁₈ -alkyl, C₅₋₁₂ -cycloalkyl,phenyl or C₇ -C₉ -aralkyl each of which is unsubstituted or issubstituted by one or two C₁ -C₁₂ -alkyl groups, or R₁₀, R₁₁ and R₁₂ areeach C₂ -C₁₀ -alkoxyalkyl or C₃ -C₂₀ -alkoxycarbonylalkyl.

The compounds of the formula IV can be produced, in a known manner (cp.Houben-Weyl "Methoden der organischen Chemie", Vol. 12/2, pp. 45-51),from the alcohols R₁ --OH and R₂ --OH, wherein R₁ and R₂ have themeanings defined in the foregoing, and phosphorus trichloride.

As far as novel compounds are concerned, subject matter of the presentinvention embraces also compounds of the formula IV wherein R₁ and R₂form a bivalent radical of the formula II, R₃, R₄, R₅ and R₆ have themeanings already defined, n is nought or 1, and R₃, if n is nought, is--CH₂ --Z in which Z is --S--R₁₀, --N(R₁₁)R₁₂, --S--P(S)(OR₁₀)₂ or aradical of the formula III, R₁₀, R₁₁ and R₁₂ have the meanings given inthe foregoing, and R₇ and R₈ independently of one another are each CN,C₂ -C₁₉ -alkoxycarbonyl, C₂ -C₁₈ -alkanoyl, or a group of the formula(R₉ O)₂ P(O)--, R₉ has the meaning given above, R₇ has the meaning givenabove and R₇ is also hydrogen, C₁ -C₄ -alkyl, cycloalkyl or phenyl.

The compounds of the formula I wherein R₁ and R₂ are a group of theformula II in which n is nought or 1, and R₃, R₄, R₅ and R₆ are, if n is1, independently of one another each hydrogen, C₁ -C₄ -alkyl, cyclohexylor phenyl, and R₃, if n is nought, is also --CH₂ --Z, in which Z is--XR₁₀, --N(R₁₁)R₁₂, --S--P(S)--(OR₁₀)₂, or a group of the formula III,whereby X, R₁₀, R₁₁ and R₁₂ have the meanings given above, and R₇ and R₈independently of one another are each NO₂, CN, C₂ -C₁₉ -alkoxycarbonyl,C₂ -C₁₈ -alkanoyl, or a group (R₉ --O)₂ --P(O)--, wherein R₉ has themeaning given above, or R₇ and R₈ together are 2-butenylene or2-pentenylene, and R₇ is also hydrogen, C₁ -C₄ -alkyl, cyclohexyl orphenyl, are novel compounds and therefore also form subject matter ofthe present invention. With regard to their respective definitions, thesymbols R₃ to R₁₂ can correspond to any one of the meanings given aboveas examples.

Compounds to be emphasised among the novel compounds are especiallythose corresponding to the formula I wherein R₁ and R₂ form a group ofthe formula II, n is 1, and R₃, R₄, R₅ and R₆ have the meanings givenabove, and R₇ and R₈ independently of one another are C₂ -C₁₉-alkoxycarbonylalkyl, C₂ -C₁₈ -alkanoyl, NO₂ or (R₉ O)₂ P(O)--, and R₇is also hydrogen or C₁ -C₄ -alkyl; and also those compounds wherein R₅,if n is nought, is --CH₂ --Z, in which Z is --XR₁₀, --N(R₁₁)R₁₂,--S--P(S)(OR₁₀)₂, or a radical of the formula III, where R₉, X, R₁₀, R₁₁and R₁₂ have the meanings given above.

The novel compounds of the formula I can of course be produced by knownmethods, for instance by reacting the appropriate chlorides of theformula IV with hydrogen sulfide in the presence of a tertiary amine,such as pyridine or triethylamine. They are however produced moreadvantageously by the "ammonia process" described above.

The novel compounds are valuable starting materials for producinglubricant-additives, fungicides and pharmaceutical substances; they arefurthermore themselves suitable as additives in mineral and syntheticlubricants since they protect the devices to be lubricated againstfrictional wear and have no corrosive action on the parts to beprotected.

Even in very small amounts, the novel compounds of the formula I areeffective as anti-wear additives in lubricants. Thus, mineral andsynthetic lubricating oil, as well as mixtures thereof, which contain0.001 to 5 percent by weight, preferably 0.02 to 3 percent by weight,relative to the lubricant, of a compound of the formula I have excellenthigh-pressure lubricating properties, which are clearly manifested inthe greatly reduced wear phenomena on the parts to be lubricated. Thelubricants concerned are commonly known to one skilled in the art, andare described for example in the "Schmiermittel Taschenbuch"("Lubricants Handbook") Hu/ thig Verlag, Heidelberg, 1974!.

The lubricating oil formulation can additionally contain other additiveswhich are added in order to improve certain basic oil properties, forexample additives such as antioxidants, metal passivators, rustinhibitors, agents for improving the viscosity index, pour-pointdepressors, dispersants/detergents, and other additives which protectagainst wear.

Examples of antioxidants are:

(a) alkylated and non-alkylated aromatic amines and mixtures thereof,for example: dioctyldiphenylamine, mono-t-octylphenyl-α- and-β-naphthylamines, phenothiazine, dioctylphenothiazine,phenyl-α-naphthylamine and N,N'-di-sec-butyl-p-phenylenediamine;

(b) sterically hindered phenols, for example:2,6-di-tert-butyl-p-cresol, 4,4'-bis-(2,6-diisopropylphenol),2,4,6-triisopropylphenol, 2,2'-thio-bis-(4-methyl-6-tert-butylphenol)and 4,4'-methylene-bis-(2,6-di-tert-butylphenol);

(c) alkyl phosphites, aryl phosphites or alkaryl phosphites, forexample: trinonyl phosphite, triphenyl phosphite and diphenyldecylphosphite;

(d) esters of thiodipropionic acid or thiodiacetic acid, for example:dilauryl thiodipropionate or dioctyl thiodiacetate;

(e) salts of carbamic and dithiophosphoric acids, for example: antimonydiamyldithiocarbamate and zinc diamyldithiophosphate; and

(f) combinations of two or more antioxidants from the above, forexample: an alkylated amine and a sterically hindered phenol.

Examples of metal passivators are:

(a) for copper, for example: benzotriazole, tetrahydrobenzotriazole,2-mercaptobenzothiazole, 2,5-dimercaptothiadiazole,salicylidene-propylenediamine and salts of salicylaminoguanidine;

(b) for lead, for example: sebacic acid derivatives, quinizarine andpropyl gallate; and

(c) a combination of two or more of the above additives.

Examples of rust inhibitors are:

(a) organic acids and their esters, metal salts and anhydrides, forexample: N-oleoyl-sarcosine, sorbitane monooleate, lead naphthenate anddodecenylsuccinic anhydride;

(b) nitrogen-containing compounds, for example:

I. primary, secondary or tertiary aliphatic or cycloaliphatic amines andamine salts of organic and inorganic acids, for example oil-solublealkyl-ammonium carboxylates, and

II. heterocyclic compounds, for example: substituted imidazolines andoxazolines;

(c) phosphorus-containing compounds, for example: amine salts ofphosphoric acid partial esters;

(d) sulfur-containing compounds, for example: bariumdinonylnaphthalene-sulfonates and calcium petroleum sulfonates; and

(e) combinations of two or more of the above additives.

Examples of agents which improve the viscosity index are for example:polymethacrylates, vinylpyrrolidone/methacrylate copolymers,polybutenes, olefine copolymers and styrene/acrylate copolymers.

Examples of pour-point depressors are for example: polymethacrylates andalkylated naphthalene derivatives.

Examples of dispersants/detergents are for example: polybutenylsuccinicacid imides, polybutenylphosphonic acid derivatives and hyperbasicsulfonates and phenolates of magnesium, calcium and barium.

Examples of other additives which provide protection against wear arefor example: compounds which contain sulfur and/or phosphorus and/orhalogen, such as vegetable oils treated with sulfur, zincdialkyldithiophosphates, tritolyl phosphate, chlorinated paraffins,alkyl disulfides and aryl disulfides.

The Examples which follow illustrate the invention.

EXAMPLE 1 2-Chloro-5-methyl-5-butoxycarbonyl-1,3,2-dioxaphosphorinane

68.70 g (0.50 mol) of phosphorus trichloride in 50 ml of toluene wereadded dropwise with vigorous stirring, in the course of 1 hour, to asolution of 95.15 g (0.50 mol) of 2,2-bis-hydroxymethylpropionic acidbutyl ester in 250 ml of toluene at 5°-10° C. The reaction mixture wassubsequently stirred for 1 hour without cooling in a water-jet vacuum,during which time a gentle flow of N₂ was fed in; the solvent was thendistilled off in vacuo (bath temperature=50° C./15-20 mm Hg), and theresidue was purified by vacuum distillation. The product obtained was inthe form of a colourless liquid; n_(D) ²⁰ =1.4701; b.p. 113°-115° C./0.1mm Hg.

Analysis: calculated: 42.4% C, 6.4% H, 12.2% P, 13.9% Cl. found: 43.0%C, 6.3% H, 12.2% P, 13.4% Cl.

EXAMPLES 2 AND 3

The compounds 2 and 3 shown below were synthetised according to Example1.

    ______________________________________                                                                               % P                                    Ex-                  b.p.        20    cal.                                   ample Compound       (°C./mm Hg)                                                                        n.sub.D                                                                             found                                  ______________________________________                                        2     2-chloro-5,5-diethoxy-                                                                       124-127° C./0.2                                                                    1.4681                                                                              10.9                                         carbonyl-1,3,2-dioxa-            11.0                                         phosphorinane                                                           3     4-chloro-3,5,4-dioxy-                                                                        102-103° C./0.4                                                                    1.5254                                                                              15.0                                         phosphorinanespiro-              15.2                                         (3-cyclohexene)                                                         ______________________________________                                    

EXAMPLE 4 2-Chloro-4-(diisooctyloxythiophosphoryl)-thiomethyl!-1,3,2-dioxaphospholan

14.82 g (0.20 mol) of freshly distilled 2,3-epoxypropanol were addedwith stirring, in the course of half an hour, to a solution of 70.92 g(0.20 mol) of dithiophosphoric acid-O,O-di-2-ethylhexyl ester in 100 mlof toluene, and the mixture was subsequently stirred for half an hour at65°-70° C. Without intermediate isolation, the addition product obtainedwas cyclised, according to Example 1, with 27.46 g (0.20 mol) ofphosphorus trichloride to give phosphorus acid diester chloride. Thesolvent was then distilled off in vacuo (bath temperature 50° C./15-20mm Hg), and the residue freed in an oil-pump vacuum from solventresidues.

Yield: 95.6 g (97% of theory) of a light-yellow liquid; n_(D) ²⁰=1.5014.

EXAMPLE 5 2-Chloro-4-isooctyloxy-carbonyl-methyl)-thiomethyl!-1,3,2-dioxaphospholane

A solution of 41.76 g (0.15 mol) of S-2,3-dihydroxypropylthioglycolicacid isooctyl ester in 100 ml of toluene was added dropwise at -10° C.in the course of 1 hour, with vigorous stirring, to a solution of 20.6 g(0.15 mol) of phosphorus trichloride and 31.87 g (0.315 mol) oftriethylamine in 100 mol of toluene. The reaction mixture wassubsequently stirred for half an hour at -10° C. and for 3 hours at roomtemperature, and the triethylamine hydrochloride which had precipitatedwas filtered off. The solvent was distilled off in vacuo (bathtemperature 30° C./1-2 mm Hg) and the residue freed in an oil-pumpvacuum from solvent residues. Yield: 44.7 g (87% of theory) of alight-yellow liquid; n_(D) ²⁰ =1.4996.

EXAMPLE 6 2-Thiono-(2H)-5,5-dimethyl 1,3,2!dioxaphosphorinane

Into a solution of 168.6 g (1.0 mol) of2-chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane in 700 ml of toluene at atemperature of ≦10° C. was fed, for about 21/2 hours with vigorousstirring, a uniform stream of hydrogen sulfide and ammonia in such amanner that no noticeable losses of gas occurred. Stirring wassubsequently maintained for 3 hours at room temperature and, after theflow of gas had been turned off, rinsing was performed for half an hourwith nitrogen. The reaction mixture was then washed four times with 500ml of water each time, dried with sodium sulfate, and the solvent wasdistilled off in vacuo. The crystalline residue obtained was thoroughlystirred up with 300 ml of petroleum ether, filtered off, washed withpetroleum ether and dried in vacuo at 50° C. until a constant weight wasattained.

Yield: 145.4 g (87% of theory) of colourless crystals, melting point83.5°-86° C., acid number 0.18 mg of KOH/g.

EXAMPLES 7-14

The Examples listed in Table 2 were synthesised according to Example 6and purified by distillation.

                                      TABLE 2                                     __________________________________________________________________________                                   Yield                                                                             % P                                        Ex.           m.p.  b.p.   D   (% of                                                                             cal.                                       No. Compound  (°C.)                                                                        (°C./mm Hg)                                                                   n.sub.20                                                                          theory)                                                                           found                                      __________________________________________________________________________    7   2-thiono-(2H)-5-                                                                        --    111-128°/0,2                                                                  1,5075                                                                            89  13,9                                           ethyl-5-butyl-1,3,2-           13,9                                           dioxaphosphorinane                                                        8   4-thiono-(4H)-3,5,4-                                                                    118-121°.sup.(1)                                                             --     --  92  15,2                                           dioxaphosphorinane-            15,1                                           spiro-(3-cyclo-                                                               hexene)                                                                   9   2-thiono-(2H)-5-me                                                                            170°/0,1.sup.(2)                                                              1,4940                                                                            73  12,3                                           thyl-5-butoxycar-              12,3                                           bonyl-1,3,2-dioxa-                                                            phosphorinane                                                             10  2-thiono-(2H)-5,5-                                                                      66,5-67,5°                                                                   --     --  96  11,0                                           diethoxycarbonyl-              11,0                                           1,3,2-dioxaphospho-                                                           rinane                                                                    11  2-thiono-(2H)-4,5-                                                                      --    84°/4                                                                         1,4996                                                                            95  20,4                                           dimethyl-1,3,2-dioxa-          20,1                                           phospholane                                                               12  2-thiono-(2H)-5-me-                                                                     77-79 --     --  85  13,6                                           thyl-5-phenyl-1,3,2-           13,6                                           dioxa-phosphorinane                                                       13  2-thiono-(2H)-5-me-                                                                     29-32 124°/0.13                                                                     --  88  15,9                                           thyl-5-propyl-1,3,2-           16,0                                           dioxaphosphorinane                                                        14  2-thiono-(2H)-5-me-                                                                     112-114.sup.(3)                                                                     --     --  96  15,7                                           thyl-5-nitro-1,3,2-            15,9                                           dioxaphosphorinane                                                        __________________________________________________________________________     .sup.(1) after recrystallisation from toluene                                 .sup.(2) molecular distillation with decomposition                            .sup.(3) after digestion with butylacetate                               

EXAMPLE 15 2-Thiono-(2H)-5,5-dimethyl-1,3,2-dioxaphosphorinane Synthesiswith pyridine as acid acceptor

Into a solution, cooled to 5° C., of 84.3 g (0.5 mol) of2-chloro-5,5-dimethyl-1,3,2-dioxaphosphorinane and 43.5 g (0.55 mol) ofpyridine in 500 ml of toluene was fed hydrogen sulfide, with cooling,until no further noticeable absorption of gas could be observed. Thepyridine hydrochloride which had precipitated was filtered off, andwashed with toluene, and the solvent was then distilled off in vacuofrom the filtrate and washing liquid. The resulting crystalline residuewas recrystallised from cyclohexane/i-propanol (2:1).

Yield: 64.1 g (77% of theory) of colourless crystals, melting point80°-84.5° C., acid number 0.28 mg of KOH/g.

A comparison of the yield using this process with the yield obtainedwith the process according to the invention described in Example 6demonstrates the superiority of the "ammonia process".

EXAMPLE 16tert-Dodecyl-/tetradecylammonium-2,2-thiono-thiol-5,5-dimethyl-1,3,2-dioxaphosphorinane

A mixture of 83.1 g (0.50 mol) of2-thiono-(2H)-5,5-dimethyl-1,3,2-dioxaphosphorinane, 16.0 g (0.50 mol)of sulfur and 97.3 g (0.50 mol) of a primarytert-dodecyl-/tetradecylamine mixture (neutral equivalent 194.7) wasslowly stirred, in the course of which the temperature rose to 70°-80°C. and a clear liquid was formed. Stirring was continued for 1 hour at80° C. and for 3 hours at 120°-130° C.

Yield: 196 g (99% of theory) of a light-yellow highly-viscous liquid.

    ______________________________________                                        Analysis                                                                              % C        % H    % N      % P  % S                                   ______________________________________                                        calculated                                                                            54.1       10.1   3.6      7.9  16.3                                  found   53.9       10.0   3.6      7.9  16.2                                  ______________________________________                                    

This Example demonstrates the use of a compound of the formula Iaccording to the invention as an intermediate. The compound according toExample 16 is suitable as an additive in lubricating oils.

EXAMPLE 17tert-Dodecyl-/tetradecylammonium-2,2-thiono-thiol-4-S-(diisoocytloxythiophosphoryl)-thiomethyl-1,3,2-dioxaphospholane

14.82 g (0.20 mol) of freshly distilled 2,3-epoxypropanol was added withstirring, in the course of half an hour, to a solution of 70.92 g (0.20mol) of dithiophosphoric acid-O,O-di-2-ethylhexyl ester in 100 ml oftoluene, and the mixture was subsequently stirred at 65°-70° C. for halfan hour. Without intermediate isolation, the addition product obtainedwas firstly cyclised according to Example 1 with 27.46 g (0.20 mol) ofphosphorus trichloride to give phosphorous acid diester chloride, andthis was further reacted according to Example 6 with hydrogensulfide/ammonia to the corresponding 2-thiono-(2H)-1,3,2!-dioxaphospholane. To the toluene solution of the product obtainedwere subsequently added, with stirring, 6.41 g (0.20 mol) of sulfur and40.3 g (0.20 mol) of a primary tert-dodecyl-/tetradecylamine mixture(neutral equivalent 201.5), and the whole was stirred at 50° C. for 2hours. After cooling of the reaction mixture, it was washed with waterand 5% sodium sulfate solution and dried with sodium sulfate, and thesolvent was distilled off in vacuo.

Yield: 134.1 g (93% of theory) of a viscous, light-yellow liquid; n_(D)²⁰ =1.5162; acid number: calculated 77.5. found 76.9.

    ______________________________________                                        Analysis         % N    % P                                                   ______________________________________                                        calculated       1.9    8.6                                                   found            2.0    8.6                                                   ______________________________________                                    

EXAMPLE 18 Thiophosphorous acid-O,O-diethyl ester

Hydrogen sulfide and ammonia were fed in a uniform stream at roomtemperature, with vigorous stirring, into a solution of 263 g (1.68mols) of phosphorous acid diethyl ester chloride (production accordingto German Offenlegungsschrift No. 2,643,442 from triethyl phosphite andphosphorus trichloride) in 1000 ml of petroleum benzine (40/60). Thereaction mixture warmed up to 40° C. and was held at this temperature bywater cooling. After completion of the reaction, flushing was carriedout with nitrogen for 3/4 of an hour with stirring. The ammoniumchloride which precipitated was filtered off, and the solvent wasdistilled off from the filtrate under reduced pressure. The residue waspurified by vacuum distillation.

Yield: 219 g (85% of theory) of colourless liquid, b.p. 77°-82° C./18-19mm Hg.

What is claimed is:
 1. A process for producing a compound of formula I##STR5## wherein R₁ and R₂ independently of one another are each C₁ -C₁₈-alkyl, C₅ -C₁₂ -cycloalkyl, phenyl or C₇ -C₉ -aralkyl each of which isunsubstituted or is substituted by one or two C₁ -C₁₂ -alkyl groups, orR₁ and R₂ are each C₂ -C₁₀ -alkoxyalkyl or C₃ -C₂₀ -alkoxycarbonylalkyl,or R₁ and R₂ together form a bivalent radical of the formula II ##STR6##wherein n is nought or 1, and R₃, R₄, R₅ and R₆ independently of oneanother are each hydrogen, C₁ -C₄ -alkyl, cyclohexyl or phenyl, and R₃,when n is nought, is also --CH₂ Z, in which Z is --XR₁₀, --N(R₁₁)R₁₂,--S--P(S)--(OR₁₀)₂ or a group of the formula III ##STR7## wherein R₁ andR₂ have the given meanings, and X is oxygen or sulfur, and R₁₀, R₁₁ andR₁₂ independently of one another are each C₁ -C₁₈ -alkyl, C₅ -C₁₂-cycloalkyl, phenyl or C₇ -C₉ -aralkyl each of which is unsubstituted oris substituted by one or two C₁ -C₁₂ -alkyl groups, or R₁₀, R₁₁ and R₁₂are each C₂ -C₁₀ -alkoxyalkyl or C₃ -C₂₀ -alkoxycarbonylalkyl, and R₇and R₈ independently of one another are each hydrogen, C₁ -C₄ -alkyl,cyclohexyl, phenyl, nitro, cyano, C₂ -C₁₉ -alkoxycarbonyl, C₂ -C₁₈-alkanoyl, or a group of the formula (R₉ --O)₂ --P(O)--, in which R₉ isC₁ -C₁₈ -alkyl, or R₇ and R₈ together are 2-butenylene or 2-pentenylene,which comprises(a) dissolving a compound of formula IV ##STR8## whereinR₁ and R₂ have the meanings given above in an inert organic solvent, (b)subjecting simultaneously the solution of step (a), with vigorousagitation at a temperature of -10° to 40° C., to gaseous ammonia andgaseous hydrogen sulfide till essentially a stoichiometric amount ofammonia and a stoichiometric amount to excess amount of hydrogen sulfideare added, and (c) isolating the product.
 2. A process according toclaim 1 for producing a compound of the formula I wherein R₁ and R₂ forma group of the formula II in which n is nought or 1, R₃, R₄, R₅ and R₆are, when n is 1, independently of one another each hydrogen, C₁ -C₄-alkyl, cyclohexyl or phenyl, and R₃, when n is nought, is also --CH₂--Z, in which Z is --XR₁₀, --N(R₁₁)R₁₂, --S--P(S)--(OR₁₀)₂, or a groupof the formula III, where X, R₁₀, R₁₁ and R₁₂ have the meanings givenabove, and R₇ and R₈ independently of one another are each NO₂, CN, C₂-C₉ -alkoxycarbonyl, C₂ -C₁₈ -alkanoyl, or a group (R₉ --O)₂ --P(O)--,in which R₉ has the above-given meaning, or R₇ and R₈ together are2-butenylene or 2-pentenylene, and R₇ is also hydrogen, C₁ -C₄ -alkyl,cyclohexyl or phenyl.
 3. A process according to claim 1 for producing acompound of the formula I wherein R₁ and R₂ independently of one anotherare each C₃ -C₁₃ -alkyl, C₆ -C₁₀ -cycloalkyl, phenyl or C₇ -C₈ -aralkyleach of which is unsubstituted or is substituted by one or two C₁ -C₄-alkyl groups, or R₁ and R₂ are each C₃ -C₆ -alkoxyalkyl or C₄ -C₁₀-alkoxycarbonylalkyl, or R₁ and R₂ together form a radical of theformula II in which R₃, R₄, R₅ and R₆ independently of one another areeach hydrogen or C₁ -C₄ -alkyl, and R₇ and R₈ independently of oneanother are each hydrogen, C₁ -C₄ -alkyl, cyclohexyl, phenyl, nitro, C₂-C₉ -alkoxycarbonyl or C₂ -C₈ -alkanoyl, or R₇ and R₈ together are2-butenylene or 2-pentenylene, and n is 0 or
 1. 4. A process accordingto claim 1 for producing a compound of the formula I wherein R₁ and R₂form a group of the formula II, n is 1, and R₃, R₄, R₅ and R₆ have themeanings given above, and R₇ and R₈ independently of one another areeach C₂ -C₁₉ -alkoxycarbonylalkyl, or together they are 2-pentenylene,and R₇ is also hydrogen or C₁ -C₄ -alkyl.
 5. A process according toclaim 1 for producing a compound of the formula I wherein R₁ and R₂together form a group of the formula II, n is nought, R₄, R₅ and R₆ havethe meanings given above, and R₃ is a group of the formula --CH₂ --Z,wherein Z is --XR₁₀, --N(R₁₁)R₁₂, --S--P(S)(OR₁₀)₂, or a group of theformula III, and X, R₁₀, R₁₁ and R₁₂ have the meanings given above.